Cathepsin C Aggravates MOG_35-55-induced Experimental Auto-immune Encephalomyelitis By Regulating Th Cells Differentiation

Background:Multiple sclerosis?MS?is a chronic autoimmune disease of the central nervous system?CNS?accompanied by inflammatory demyelination,axonal damage,activation of glial cells and immune cell infiltration.Myelin oligodendrocyte glycoprotein?MOG?induced experimental autoimmune encephalomyelitis?EAE?is the most common model for MS,which is mainly mediated by autoantigen-specific CD4+T cells that play an important role in modulating immune responses.Upon antigenic stimulation,Na?ve CD4+T cells can differentiate into Th1,Th17 and Tfh cells which mainly play pro-inflammatory role,and Th2 and Treg subtype cells which have anti-inflammatory function.Cathepsin C?CatC?,which is a lysosomal cysteine protease and mainly expresses in microglia in the CNS,has been demonstrated that can aggravate demyelination status in cuprizone and EAE animal model through increasing inflammatory cell infiltration and expression of chemokines in the CNS.Despite intensive years of research,CatC can exacerbate LPS-induced inflammation by promoting microglia and macrophage M1 polarization in the innate immune response,while the function of CatC on adaptive immune response especially on inflammatory demyelination of EAE regulated by autoimmune reaction have not been elucidated clearly.Objective:Investigate the effect of CatC on neuropathological status of EAE and its related adaptive immunological mechanism.Method:MOG_35-55induced EAE model were established by using C57BL/6 J wildtype?WT?and CatC overexpression?CatCOE?mice,respectively.After immunization,the clinical score was used to value the severity of MOG_35-55-induced EAE model?range from0-5?.At 7 days,10 days,14 days,23 days and 50days after immunization,a single cell suspension created from spleen and draining lymph node of EAE model mice was stained with anti-CD3,anti-CD4,anti-IFN?,anti-IL-4,anti-IL-17,anti-CXCR5,anti-PD-1,anti-CD25 and anti-Foxp3 antibodies,respectively.Then,the cells frequencies of Th1,Th2,Th17,Treg and Tfh were analyzed by flow cytometry.The concentrations of IL-21,IL-17and MOG_35-55specific Ig G were measured by ELISA.Result:The clinical scores in CatCOE mice are significantly higher than that in WT mice during the onset and persistent stage of EAE model,when auto adaptive immune response mainly occurs in both the periphery and the CNS,implying the overexpression of CatC aggravates EAE through its function on effecting autoimmune reaction.Furthermore,at 7 days,10 days and 14days after immunization,the frequency of Tfh and Th17 cells in spleen was significantly higher in CatCOE mice compared with that in WT mice,while CatC had no effect on Th1,Th2 and Treg cells differentiation,suggesting CatC may aggravate MOG_35-55-induced EAE by increasing the differention of Tfh and Th17 cells.The frequency of Tfh and Th17 cells in cervical lymph nodes was also higher in CatCOE mice compared with that in WT mice.And the expression of Bcl-6 and Rorc m RNA in brain was significantly higher in CatCOE mice compared with that in WT mice.Simultaneously,IL-21 produced by Tfh cells which could direct B cell differentiation,germinal center formation and immunoglobulin class switching was significantly increased.IL-17A produced by Th17 cells that could elevate the numbers of B cells and the levels of CXCL13 in Th17-EAE mice also augmented markedly,Furthermore,There was a marked increase in MOG_35-55-specific Ig G in CatCOE mice compared with WT mice.Conclusion:CatC exacerbates the progression of EAE disease by promoting thedifferentiation of CD4+T cells into Th17 and Tfh cells,and increase their related cytokines IL-17 and IL-21 expression and the production of MOG_35-55-specific Ig G antibodies.